Rooftop Advertising for Satellite Images

With technologies like Google and Yahoo Maps and Google Earth, utilities that use very hi-res satellite images, it's time to start advertising on rooftops. I have been saying this for over a year now, ever since I first experienced Google Earth, and I remember the moment it became obvious: I was sitting on my girlfriend's porch, from which you can see the enormous roof of a Wal-Mart. Why not throw a logo up there? With the rising adoption of these technologies by news corporations and general internet users, a mainstream vehicle is already in place. And with most business rooftops being flat and white, the venue is already in place. All you need is the paint and labor to put your logo up there, or you could sell your space, and therefore, the cost effectiveness is there. Plus, you don't owe anyone for it. One method of surprisingly effective advertising is simple exposure, and with a continually segmenting market and a growing online market, I'm surprised this hasn't already taken off.